Disc Brake Conversion "Right Stuff" - Pontiac GTO Forum
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post #1 of 7 (permalink) Old 02-11-2019, 09:05 AM Thread Starter
 
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Disc Brake Conversion "Right Stuff"

Good Morning,
I am working on a disc brake conversion from the "Right Stuff" when I installed the new spindle I seem to have a geometry issue with the upper ball joint. I thought it was because I had no weight on the car but that did not help once I dropped it down. Has anyone else used their conversion and run into issues. When I look at the old spindle it appears to be about 1/2 inch longer from backing plate to center of the ball joint hole.
FYI 1969 GTO.
Thoughts anyone?
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post #2 of 7 (permalink) Old 02-11-2019, 11:26 AM
 
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Just a guess here, but I've read that some disc brake conversion kits include a "lowering " spindle to drop the car down 2-3". Maybe this is what you have. A check-in with the Right Stuff to see if this is the case and maybe an exchange could be done.
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post #3 of 7 (permalink) Old 02-11-2019, 06:19 PM
 
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Not being a suspension expert, but depending on the conversion kit and what spindle they use, you may need to use the aftermarket tubular upper control arm which can be longer in length from the frame mounting to the ball joint.

I have read this needs to be done to correct the geometry when using the later 1973 and up Lemans disc brake conversions as the '73 and up had a redesigned front end to go with the redesign of the car. No doubt other GM platforms of the same body type would also throw off the geometry if used. So this may be the issue?

A friend of mine has a 1970 Camaro which is lowered and he used the factory lower A-arm and had to go with the tubular upper A-arm - which I thought odd, but maybe why he did it so he could get the geometry of the front end correct.
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post #4 of 7 (permalink) Old 02-12-2019, 07:36 AM
 
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It seems to be a drop spindle and the coil spring height is not helping to let the car drop down to the point where the upper balljoint stud reaches a vertical alignment.

You can take the drum brake spindle and cut down its upper threaded bolt boss and that way it will let you attach the caliper bracket and the whole disc brake assembly.

Also, perhaps you'll have to resize your Pontiac spindle two lower bolt threads to use the new bolts.
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post #5 of 7 (permalink) Old 02-12-2019, 09:59 AM
 
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I have the Right Stuff conversion on my 66 Lemans,....could be a bit different or a bit different kit....but it looks like just negative camber, a tilt in of the wheel as part of alignment geometry.

When you put these kits on you have to realign,...when add or take away shims on the top of the upper control are it will increase or decrease camber...I do myself but a shop can do it for you. It takes special tools. Depending on the A Arm you add or remove shims to increase positive camber.....you have negative camber in the photo, an inward tilt at the top.

There is a factory alignment spec and you add or subtract shims to get it right. It can move out a bit with camber adjustment,...

Could be something else, but looks like too much negative camber.
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post #6 of 7 (permalink) Old 02-14-2019, 06:39 AM Thread Starter
 
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Thanks, I thought of that also, to increase positive camber I would remove shims correct? Problem is I only have two shims in now, not sure it will make more than 1/2 a degree difference but I will try. I also just read something about installing an off set upper control arm rod, it is actually angled and gives up to two degrees of additional camber. Still have not heard back from Right Stuff so their customer service is not great.
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post #7 of 7 (permalink) Old 02-14-2019, 07:23 AM
 
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Yes, you can get a shim pack at the local auto parts or summit or JEGS,...try 2 real thin shims, donít use no shims....see if you can get close, that custom Adjustment arm should bring it in for sure, just give you more room.

Sometimes these shim bolts are not tightened up and torqued properly. Try thin shims torque it up maybe you can can get it in specs.

That what it appears to me. I donít recall the spec but I think it has a slight negative camber. It has to be checked with wheel on the ground and you really need a turntable or a slip plate at least to get the wheel to sit right. Two pieces of thin plywood with some grease in the middle when you set it down gently to check you angles.

If you can get it close then take it to alignment shop, you need a turntable to get the caster right.

The good news, should not be anything not doable! Good luck and let us know how you do!
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